text: /*
   * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
   *
   * SPDX-License-Identifier: Unlicense OR CC0-1.0
   */
  #include "freertos/FreeRTOS.h"
  #include "freertos/task.h"
  #include "esp_check.h"
  #include "esp_sleep.h"
  #include "soc/uart_pins.h"
  #include "driver/uart.h"
  #include "driver/gpio.h"
  
  #define EXAMPLE_UART_NUM        0
  /* Notice that ESP32 has to use the iomux input to configure uart as wakeup source
   * Please use 'UxRXD_GPIO_NUM' as uart rx pin. No limitation to the other target */
  #define EXAMPLE_UART_TX_IO_NUM  U0TXD_GPIO_NUM
  #define EXAMPLE_UART_RX_IO_NUM  U0RXD_GPIO_NUM
  
  #define EXAMPLE_UART_WAKEUP_THRESHOLD   3
  
  #define EXAMPLE_READ_BUF_SIZE   1024
  #define EXAMPLE_UART_BUF_SIZE   (EXAMPLE_READ_BUF_SIZE * 2)
  
  static const char *TAG = "uart_wakeup";
  
  static QueueHandle_t uart_evt_que = NULL;
  
  static void uart_wakeup_task(void *arg)
  {
      uart_event_t event;
      if (uart_evt_que == NULL) {
          ESP_LOGE(TAG, "uart_evt_que is NULL");
          abort();
      }
  
      uint8_t* dtmp = (uint8_t*) malloc(EXAMPLE_READ_BUF_SIZE);
  
      while(1) {
          // Waiting for UART event.
          if(xQueueReceive(uart_evt_que, (void * )&event, (TickType_t)portMAX_DELAY)) {
              ESP_LOGI(TAG, "uart%d recved event:%d", EXAMPLE_UART_NUM, event.type);
              switch(event.type) {
                  case UART_DATA:
                      ESP_LOGI(TAG, "[UART DATA]: %d", event.size);
                      uart_read_bytes(EXAMPLE_UART_NUM, dtmp, event.size, portMAX_DELAY);
                      ESP_LOGI(TAG, "[DATA EVT]:");
                      uart_write_bytes(EXAMPLE_UART_NUM, (const char *)dtmp, event.size);
                      break;
                  // Event of HW FIFO overflow detected
                  case UART_FIFO_OVF:
                      ESP_LOGI(TAG, "hw fifo overflow");
                      // If fifo overflow happened, you should consider adding flow control for your application.
                      // The ISR has already reset the rx FIFO,
                      // As an example, we directly flush the rx buffer here in order to read more data.
                      uart_flush_input(EXAMPLE_UART_NUM);
                      xQueueReset(uart_evt_que);
                      break;
                  // Event of UART ring buffer full
                  case UART_BUFFER_FULL:
                      ESP_LOGI(TAG, "ring buffer full");
                      // If buffer full happened, you should consider encreasing your buffer size
                      // As an example, we directly flush the rx buffer here in order to read more data.
                      uart_flush_input(EXAMPLE_UART_NUM);
                      xQueueReset(uart_evt_que);
                      break;
                  // Event of UART RX break detected
                  case UART_BREAK:
                      ESP_LOGI(TAG, "uart rx break");
                      break;
                  // Event of UART parity check error
                  case UART_PARITY_ERR:
                      ESP_LOGI(TAG, "uart parity error");
                      break;
                  // Event of UART frame error
                  case UART_FRAME_ERR:
                      ESP_LOGI(TAG, "uart frame error");
                      break;
                  // ESP32 can wakeup by uart but there is no wake up interrupt
  #if SOC_UART_SUPPORT_WAKEUP_INT
                  // Event of waking up by UART
                  case UART_WAKEUP:
                      ESP_LOGI(TAG, "uart wakeup");
                      break;
  #endif
                  default:
                      ESP_LOGI(TAG, "uart event type: %d", event.type);
                      break;
              }
          }
      }
      free(dtmp);
      vTaskDelete(NULL);
  }
  
  static esp_err_t uart_initialization(void)
  {
      uart_config_t uart_cfg = {
          .baud_rate  = 115200,
          .data_bits  = UART_DATA_8_BITS,
          .parity     = UART_PARITY_DISABLE,
          .stop_bits  = UART_STOP_BITS_1,
          .flow_ctrl  = UART_HW_FLOWCTRL_DISABLE,
          .source_clk = UART_SCLK_DEFAULT,
      };
      //Install UART driver, and get the queue.
      ESP_RETURN_ON_ERROR(uart_driver_install(EXAMPLE_UART_NUM, EXAMPLE_UART_BUF_SIZE, EXAMPLE_UART_BUF_SIZE, 20, &uart_evt_que, 0),
                          TAG, "Install uart failed");
      ESP_RETURN_ON_ERROR(uart_param_config(EXAMPLE_UART_NUM, &uart_cfg), TAG, "Configure uart param failed");
      ESP_RETURN_ON_ERROR(uart_set_pin(EXAMPLE_UART_NUM, EXAMPLE_UART_TX_IO_NUM, EXAMPLE_UART_RX_IO_NUM, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE),
                          TAG, "Configure uart gpio pins failed");
      return ESP_OK;
  }
  
  static esp_err_t uart_wakeup_config(void)
  {
      /* UART will wakeup the chip up from light sleep if the edges that RX pin received has reached the threshold
       * Besides, the Rx pin need extra configuration to enable it can work during light sleep */
      ESP_RETURN_ON_ERROR(gpio_sleep_set_direction(EXAMPLE_UART_RX_IO_NUM, GPIO_MODE_INPUT), TAG, "Set uart sleep gpio failed");
      ESP_RETURN_ON_ERROR(gpio_sleep_set_pull_mode(EXAMPLE_UART_RX_IO_NUM, GPIO_PULLUP_ONLY), TAG, "Set uart sleep gpio failed");
      ESP_RETURN_ON_ERROR(uart_set_wakeup_threshold(EXAMPLE_UART_NUM, EXAMPLE_UART_WAKEUP_THRESHOLD),
                          TAG, "Set uart wakeup threshold failed");
      /* Only uart0 and uart1 (if has) support to be configured as wakeup source */
      ESP_RETURN_ON_ERROR(esp_sleep_enable_uart_wakeup(EXAMPLE_UART_NUM),
                          TAG, "Configure uart as wakeup source failed");
      return ESP_OK;
  }
  
  esp_err_t example_register_uart_wakeup(void)
  {
      /* Initialize uart1 */
      ESP_RETURN_ON_ERROR(uart_initialization(), TAG, "Initialize uart%d failed", EXAMPLE_UART_NUM);
      /* Enable wakeup from uart */
      ESP_RETURN_ON_ERROR(uart_wakeup_config(), TAG, "Configure uart as wakeup source failed");
  
      xTaskCreate(uart_wakeup_task, "uart_wakeup_task", 4096, NULL, 5, NULL);
      ESP_LOGI(TAG, "uart wakeup source is ready");
      return ESP_OK;
  }
  